1. Field of the Invention
The present invention relates to an air bag apparatus assembled in a steering wheel or the like of a vehicle and which develops and inflates a bag body in a direction toward a vehicle occupant to protect that vehicle occupant.
The present invention, while explained with reference to an embodiment of an air bag apparatus for a steering wheel, it can be equally applied to other air bag apparatus for an assistant driver""s seat or a rear seat having a similar structure.
In this specification, each of the terms xe2x80x9cverticalxe2x80x9d, xe2x80x9clateralxe2x80x9d and xe2x80x9clongitudinalxe2x80x9d, which shows a relationship between positions means a relative relationship between positions from a viewpoint in front view of the steering wheel with the vehicle going straight ahead.
2. Description of Related Art
Air bag apparatus usually includes an inflator, an air bag mounted to the inflator in a folded state, from an original circular shape, and a cover for covering the folded bag body. The cover is provided with a hinged door portion which opens by a force applied at a time when the air bag is initially developed and inflated.
On the basis of the present demand, in which the air bag of the air bag apparatus is preferentially developed and inflated in a vertical direction, an example of such, an air bag apparatus is described in Japanese Patent Publication No. 7-110600.
This air bag apparatus for a driver""s seat is mounted to a substantially central portion of a steering wheel and comprised an inflator for generating a gas for developing an air bag. The air bag is arranged in a folded body state and surrounds a gas injection hole of the inflator, it has a circular shape when inflated and is covered by a cover member capable of suddenly breaking open.
The cover member included an upper flap which opens to an upper side of the steering wheel and a lower flap which opens to a lower side of the steering wheel.
In some cases a center line which agrees with the direction in which the upper and lower flaps of the cover member are broken and developed, passes through a center point of the air bag is defined as Y, and that a center line which crosses the center line Y in a perpendicular direction and passes through a center point of the air bag is defined as X,
The air bag is formed with a long and narrow shape in the Y direction by folding right and left side surfaces disposed in right and left side of the center line Y to a side of the seated occupant along a first folding line parallel to the center line Y.
Each of the side surfaces of the long and narrow shape, disposed in both side of the center line X, is folded to the side of the seated occupant along a second folding line parallel to the center line X so as to form the folded body having an upper surface and a lower surface which respectively open in an upper direction and a lower direction at an initial time of developing.
However, as a result of inflation testing of the foregoing air bag apparatus performed by the inventors of the present invention, it is found that there is a fast a change of the speed of an inflation between the time when the air bag body is in a middle position and when the air bag body is completely inflated (hereinafter refer to xe2x80x9cinflation speed in the middle portion heightxe2x80x9d).
Though it is necessary for the air bag body to completely inflate within a predetermined time, it is preferable that the inflation speed be slow in the middle portion until full inflation is completed.
The present invention is made by taking the above described problems into consideration and an object of the present invention is to provide an air bag apparatus which can limit the inflation speed in the middle portion at a time when the air bag apparatus is operated.
Another object of the present invention is, in addition to the above object, to provide an air bag apparatus which can preferentially develop and inflate an air bag body in a vertical direction relative to a front to rear axis.
One aspect of the present invention solves the above first object in accordance with the following structure. On an air bag apparatus which is assembled in a steering wheel or the like of a vehicle and which develops and inflates an air bag in a direction toward a vehicle occupant at a time of operation. The air bag apparatus comprises an inflator, an air bag or bag body which is mounted substantially at a center of an upper surface of the inflator in a folded state and a cover for covering the folded bag body. The cover body is provided with a hinged door portion which is opened by a force applied at a time when the bag body is initially developed and inflated. The air bag body is folded to a direction so as to be formed with a long and narrow shape having a predetermined width and both end portions of the long and narrow shape are housed within a housing space formed by the inflator and the cover body in a state of an outwardly winding roll.
In the above structure, it is preferable that the housing space is provided with an overhang portion which covers a front surface of the outwardly winding roll close to an outer side.
It is preferable that the overhang portion is formed by a door adjacent portion which is disposed adjacent to right and left outer side of the hinged door portion in the cover body.
In the above structure, it is preferable that the cover body is provided with a breakage prescribed portion having a H-shaped front view in a state of going straight ahead of the vehicle, the hinged door portion is formed as a double-leafed hinged door in the vertical direction, and the outer ends of the outwardly winding roll are positioned outside of right and left sides of the H-shaped breakage prescribed portion having a thin thickness so as to achieve the object of preferentially develop and inflate the vertical direction of the air bag body in the front view at a state of going straight ahead of the vehicle.
Further, in the structure in which a bag holder for holding the bag body is provided with a side wall projecting to the cover body, the overhang portion may be formed by a side wall extending portion which is formed by extending the side wall to an inner direction, and in the structure in which the side wall is provided with a metal projecting portion in an inner side thereof and a bag protecting plate is mounted to an inside of the metal projecting portion, the overhang portion may be formed by a protecting plate extending portion which is formed by extending the bag protecting plate to an inner direction.